During drug delivery, it is often desirable to bypass the digestive system of a patient to avoid degradation of the drug's active ingredients that can be caused by the catalytic enzymes in the digestive tract and liver. Delivery of a drug other than by way of the intestines is known as parenteral delivery. Parenteral delivery of drugs in liquid form is often desired to enhance the effect of the substance being delivered, insuring that the unaltered medicine reaches its intended site at a significant concentration. Moreover, undesired side effects associated with other routes of delivery, such as systemic toxicity, can potentially be avoided by parenteral delivery. Further, many medicines are only available in liquid form, and/or the liquid may have desirable characteristics that cannot be achieved with solid or pill form. Delivery of liquid medicines may best be accomplished by infusing directly into the cardiovascular system via veins or arteries, into the subcutaneous tissue, or directly into organs, tumors, cavities, bones, or other site-specific locations within the body.
Parenteral delivery of liquid medicines into the body is often accomplished by administering bolus injections using a needle and reservoir or continuously by gravity driven dispensers or transdermal patch technologies. Bolus injections often imperfectly match the clinical needs of the patient and usually require larger individual doses than are desired at the specific time they are given. Continuous delivery of medicine through gravity feed systems compromise the patient's mobility and lifestyle and limit the therapy to simplistic flow rates and profiles. Transdermal patches have special requirements of the medicine being delivered, particularly as it relates to the molecular structure, and similar to gravity feed systems, the control of the drug administration is severely limited.
Ambulatory infusion pumps have been developed for delivering liquid medicaments to a patient. These infusion devices have the ability to offer sophisticated fluid delivery profiles that can provide bolus delivery, continuous infusion, and variable flow rate delivery. Ambulatory infusion pumps, however, can be problematic, as the user is generally forced to choose between a soft delivery cannula, which tends to have high initial failure rates and is prone to kinking, or a steel needle set, which has a lower initial failure rate but is associated with increased pain and shortened time of use. Additionally, the challenge with current infusion sets is that the 90-degree (i.e., rigid cannula) infusion sets, which are easiest to insert, are also associated with the highest rates of failure, partially due to needle breakage and/or fluid leaking out of the relatively short insertion path. Further, infusion sets with a soft cannula, however, tend to be harder to insert and/or are associated with increased apprehension/intimidation.
Moreover, a necessary and important step in preparing an infusion set for use is filling the tubing with liquid medicament, such as insulin to be delivered to a person with diabetes. This is often done by attaching the infusion set tubing to either the insulin pump reservoir or the insulin pump reservoir adaptor (e.g., a device that holds the reservoir into the pump). The pump is then programmed to fill the tubing with insulin. This is not an automatic process. The user is typically either asked to hold down a button until the tubing is filled or to program an amount believed to be sufficient to fill the tubing. The user is instructed not to move on to another step until they observe insulin drops exiting the distal end of the tubing to infusion site connection or the distal end of the infusion cannula. The observation confirms that the tubing has been filled.
Tube filling carries two risk cases. The first risk case is when the user attempts to fill the tube and makes the mistake of connecting the tube to an infusion set that has already been inserted into their body. This would prevent the user from knowing when the tube had been completely filled and would result in any excess insulin delivered in an attempt to fill the tube to be delivered to the pump user, resulting in an over delivery. Over delivery carries with it a significant risk of hypoglycemia (low blood glucose levels). The second risk case is incomplete filling of the tubing. Failure to completely fill the tubing can lead to under delivery of insulin. This in turn can lead to hyperglycemia (elevated glucose levels). The amount of missed insulin (10 to 15 units) can be approximately 25 to 50% of a typical pump user's daily dose (˜42 units) but could exceed the total daily dose of a pump user with higher than typical insulin sensitivity. In many cases, the missed insulin associated with a non-filled or partially filled tube causes a significant health risk to the pump user. Filling the tubing is not an easy task, especially for those with any macular degeneration, as is often associated with diabetes progression.
Accordingly, an ambulatory infusion pump set that is efficient, safe, effective, easy to insert into a patient, and easy/safe to fill is desired.